The UV absorbers of the 2H-benzotriazole and benzophenone types have long been known as very effective light stabilizers for a host of organic materials and have enjoyed considerable commercial success. Recently, the long known s-triazine UV absorbers have been shown to exhibit particularly good thermal stability in addition to their light stabilization efficacy.
U.S. Pat. Nos. 3,004,896; 3,055,896; 3,072,585; 3,074,910; 3,230,194; 4,127,586; 4,226,763; 4,278,589; 4,315,848; 4,383,863; 4,675,352; 4,681,905 and 4,853,471 describe the preparation and uses of the 2H-benzotriazole UV absorbers.
The description, preparation and uses of the benzophenone UV absorbers are found in a comprehensive review by G. R. Lapin in the "Encyclopedia of Polymer Science and Technology", N. Bikales, editor, John Wiley-Interscience, New York, Vol. 14, 1971, pp 125-148.
s-Triazine UV absorbers are described in U.S. Pat. Nos. 5,376,710; 5,369,140; 5,364,749; 5,354,794; 5,350,449; 5,322,868; 5,300,414; 5,298,067; 5,298,030; 5,288,778; 5,106,972; 5,106,891; 5,096,489; 5,084,570; 4,962,142; 4,950,304; 4,831,068; 4,826,978; 4,740,542; 4,619,956; 4,355,071 and 3,843,371; as well as copending application Ser. Nos. 08/143,525; 08/281,381; 08/463,140; 08/463,569; 08/463,572 and 08/463,573; and EP 557,247; 506,615; 483,488; 468,921; 444,323; 442,847; 434,608; 280,653; 205,493; 200,190 and 165,608; as well as WO94/05645.
In many instances, the s-triazine, benzotriazole and/or benzophenone UV absorbers exhibit limited compatability with certain substrates and/or an excessive tendency to exude, sublime or volatilize away during processing of stabilized compositions into sheets, films or other pellicles when processing is done at elevated temperatures as described in U.S. Pat. Nos. 3,268,474; 3,244,708; 3,242,175 and 3,188,887. Likewise, such compounds may also suffer undue loss by volatilization or sublimation from fabricated structures, particularly thin films, coatings or fibers, when such structures are subjected to elevated temperatures during use.
Attempts have been made to increase compatibility and/or reduce volatility by modifying the structure of these UV absorbers. Hybrid products of benzophenones and benzotriazoles have been reported and an example of such a UV absorber useful in the range of 240-420 nm is described in EP 431,868, namely 3,5-bis(2H-benzotriazol-2-yl)-2,4,4'-trihydroxybenzophenone.
EP 613,891 teaches that hybrid products such as 2-(benzotriazol-2-yl)-4-alkyl-6-(2-hydroxy-3-benzoyl-6-alkoxy-benzyl)pheno ls are prepared by reacting a Mannich base of 2-(2-hydroxy-5-alkylphenyl)-2H-benzotriazole with a 2-hydroxy-4-alkoxybenzophenone. The hybrid products exhibit outstanding efficacy in protecting organic substrates from light induced deterioration as well as good resistance to loss by volatilization or exudation during process of stabilized compositions at elevated temperatures.
U.S. Pat. No. 3,230,194 teaches that substitution of a higher alkyl group such as tert-octyl for a lower alkyl group such as methyl improves compatibility and performance of substituted benzotriazole UV absorbers in polyethylene.
Likewise, U.S. Pat. Nos. 4,278,590; 4,283,327 and 4,383,863 show that 2-(2-hydroxy-3,5-di-tert-octylphenyl)-2H-benzotriazole exhibits and excellent combination of compatibility with and/or solubility in numerous polymer substrates along with superior resistance to loss from volatilization during high temperature processing, in end-use application where coatings or films of the stabilized compositions are exposed to ambient weathering and actinic light, and in photographic applications.
U.S. Pat. No. 4,675,352 teaches that liquid benzotriazole UV absorbers of low volatility are prepared by the alkylation of preformed 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole.
U.S. Pat. Nos. 3,936,305; 4,681,905; 4,684; 4,684,679 and 5,108,835 disclose 2,2'-methylene-bis[4-hydrocarbyl-6-(benzotriazol-2-yl)phenols] having high molar activities and low volatility.
U.S. Pat. Nos. 3,399,237 and 4,169,089; Japanese Sho 53-113849; 57-6470; 49-78692; 50-74579 and 50-86487 teach the corresponding class of low volatility compounds with high molar activities which are the methylene-bis(2-hydroxybenzophenones).
U.S. Pat. No. 5,166,355 describes a process for making 2,2'-methylene-bis[6-(2H-benzotriazol-2-yl)-4-hydrocarbylphenol] or 5,5'-methylene-bis(2-hydroxy-4-alkoxy-benzophenone) using bis(dialkylamino)methane.
The instant compounds are structurely distinguished from each of the compounds of the prior art and said instant compounds exhibit decreased volatility and an unexpected enhancement of their absorption characteristics over a particularly broad ultraviolet range. Their photographic inertness is particularly valuable for their use in photographic compositions, especially in protecting color dye images against the harmful effects of actinic light.